Low molecular weight copolymer amides

ABSTRACT

A low molecular weight copolymer reaction product of a copolymer acid of an α-olefin and an unsaturated carboxylic acid, preferably an α,β-ethylenically unsaturated carboxylic acid, and at least one amino acid compound. The present invention includes a method of preparing the copolymer reaction product. The reaction product has excellent compatibility with other polymers, particularly polyamides. The copolymer reaction product is useful in a method to flush water from pigments.

This application is a continuation of application Ser. No. 08/483,492Filed Jun. 7, 1995, now abandoned, which is a division of applicationSer. No. 08/280,292, filed Jul. 26, 1994 (now abandoned) which is acontinuation of application Ser. No. 08/088,485, filed Jul. 7, 1993 (nowabandoned) which is a continuation of application Ser. No. 07/938,319,filed Aug. 31, 1992 (now abandoned) which is a continuation ofapplication Ser. No. 07/452,527 filed Dec. 18, 1989 (now abandoned).

BACKGROUND OF THE INVENTION

1. Field of Invention

This invention is in the field of low molecular weight olefincopolymers; more particularly, this invention relates to low molecularweight copolymers of an α-olefin and an unsaturated carboxylic acid,preferably an α,β-ethylenically unsaturated carboxylic acid having up to100 percent of the carboxylic acid groups reacted with at least oneamino acid. The reaction product is useful for flushing pigments.

2. Description of Related Art

The process of flushing pigments is reviewed in Great Britain Patent No.915,453, and by Apps, Printing Ink Technology, Chemical Publishing Co.,Inc., NY, pp.498-500 (1959). Flushing is a process to prepare pigmentdispersions in which the pigments remain finely divided and in asuitable form for further processing such as incorporation intopolymeric compositions and inks.

During the manufacture of pigments an aqueous mass of pigment isproduced. The removal of all of the water can result in the pigmentsagglomerating. Some of the water is removed leaving the finely dividedpigment as a wet cake. The aqueous mass of pigment is mixed with apolyolefin usually of low molecular weight. The mixture is coagulatedand the aqueous phase is removed, typically by heating the composition,optionally in a vacuum. The pigment is dispersed in the low molecularweight polymer which can optionally be pulverized.

Low molecular weight polyethylene waxes are used to flush pigments. Theflushed pigments are useful in polymeric compositions used for fibers,molding compounds, extrusion compounds, sheets, film, and the like.Flushed pigments have been used in compositions based on polyethylene,polyvinylchloride, ABS, polyamides, and polycarbonates, among other.

Low molecular weight olefinic copolymers, particularly low molecularweight ethylene copolymers, are described in U.S. Pat. No. 3,658,741.This patent discloses homogeneous copolymers of ethylene and variouscomonomers including unsaturated acids and their derivatives, such asesters and amides. Examples of the derivatives include methyl acrylate,methyl methacrylate, ethyl acrylate, and dimethylaminoethylmethacrylate.

U.S. Pat. No. 4,381,378 discloses a method for the preparation of lowmolecular weight copolymer salts from low molecular weight copolymeracids of α-olefins and α,β-ethylenically unsaturated carboxylic acids.Preferred copolymers are copolymers of ethylene and acrylic acid.

U.S. Pat. Nos. 4,412,040 and 4,603,172 disclose low molecular weightcopolymer salts for use as lubricants and dispersion aides in plastics.The disclosed salts include salts of low molecular weight copolymers ofα-olefins and α,β-ethylenically unsaturated carboxylic acids. Preferredcopolymers are copolymers of ethylene and acrylic acid.

U.S. Pat. Nos. 3,388,186 and 3,465,059 disclose polyamide compositions.The compositions are made by grafting amino acids or lactams onto abackbone chain containing recurring ethylenic units and reactive sites,such as carboxyl radicals of acid, ester or salt groups, andparticularly acrylic acid esters. The proportion of the copolymerbackbone to the polyamide graft can vary between 2 and 90 percent. Thecopolymers disclosed for use as part of the backbone chain have a numberaverage molecular weight of at least about 13,700 in U.S. Pat. No.3,388,196; and at least 10,000 in U.S. Pat. No. 3,465,059.

U.S. Pat. No. 3,634,543 discloses nucleated graft polymers ofpolycaprolactam on carboxy containing copolymeric backbone. The graftpolymer is prepared by polymerization of caprolactam in the presence ofa copolymer of an olefin and an unsaturated carboxylic acid.

U.S. Pat. No. 4,035,438 discloses an impact resistant mixture ofpolyethylene; a graft polymer of an ethylene/acrylic acid copolymer orethylene/methacrylic acid copolymer as a graft substrate and graftedpolymerised units of ε-caprolactam; and polycaprolactam. The copolymersfor use as graft substrates are those which contain 1 to 10 mol percentof (meth)acrylic acid, preferably from 30 percent to 70 percent in theform of the sodium salt.

SUMMARY OF THE INVENTION

It is desirable to have a low molecular weight copolymer havingstructural groups which enhance compatibility with other polymers,particularly other polymers having a higher molecular weight than thelow molecular copolymer. In accordance with the present invention, a lowmolecular weight copolymer with carboxyl groups is reacted with at leastone amino acid compound. This increases the compatibility of thereaction product with polymers such as polyamides.

The preferred low molecular weight copolymer reaction product is derivedfrom a copolymer acid of an α-olefin and an unsaturated carboxylic acid,preferably an α,β-ethylenically unsaturated carboxylic acid. The acidcopolymer has a number average molecular weight of from about 500 toabout 6,000. Preferably, the low molecular weight copolymer acid is acopolymer of ethylene and acrylic acid or methacrylic acid, having anumber average molecular weight of from about 1,000 to about 3,500. Thecopolymer acid has preferably from about 0.8 to about 35, and preferablyfrom 5 to 25 weight percent of the comonomer acid with a correspondingamount of α-olefin.

Up to 100, preferably from about 10 to 100, and more preferably fromabout 50 to 100 percent, of the carboxylic acid groups are reacted withat least one amino acid compound. The amino acid compound has an amineend group and a carboxylic acid end group. The amine end group reactswith the carboxyl end group of the copolymer acid to form an amide groupat the reaction site. There is from about 0.1 to about 50, preferablyabout 0.1 to about 40, more preferably about 0.5 to about 30, and mostpreferably about 5 to 25 weight percent based on the weight of thecopolymer reaction product of the amide chain derived from the aminoacid compound. The amide chain can be from about 10 to about 30 or about0.1 to about 10 weight percent of the reaction product group dependingon the desired properties.

The average amide chain length reacted at each carboxyl site ispreferably from about 1 to about 250, preferably 1 to 200, with specificembodiments including amide chain lengths of from 1 to 10, and 1 to 5amide groups. There can be longer amide chain lengths of from 100 to 250amide groups. Preferably, there are sufficient amide grafts, ofsufficient length to confer compatibility of the copolymer reactionproduct and another polymer, preferably polyamide. For the purpose ofthe present invention amino acid compounds include cyclic amides, i.e.,lactams which can be hydrolized to form an amino acid compound. Apreferred amino acid compound has the formula H₂ NCH₂ (CH₂)_(n) COOHwhere n is from 0 to 12, and more preferably from 4 to 8. The mostpreferred amino acid is amino caproic acid or its lactam, caprolactam.

The present invention includes a method of preparing the above recitedcopolymer reaction product comprising the steps of heating the copolymerof the α-olefin and the unsaturated carboxylic acid, preferably theα,β-ethylenically unsaturated carboxylic acid, to from about 110° C. toabout 300° C., preferably about 150° C. to about 275° C., and morepreferably about 200° C. to about 275° C.; adding a sufficient amount ofat least one amino acid compound to react with up to 100 percent of thecarboxylic acid groups; and conducting reaction of the copolymer and theacid. Preferably, the copolymer acid is preheated to from 110° C. to200° C. and more preferably, 125° C. to 175° C. The reaction ispreferably conducted under an inert atmosphere, such as nitrogen orargon, or under a vacuum.

The present invention also includes a polymer composition and apigmented composition. The polymer composition comprises at least onefirst polymer, preferably a polyamide and the above recited reactionproduct. The pigment composition comprises a pigment, at least onesecond polymer comprising the above recited copolymer reaction product,and optionally, at least one first polymer. The first polymer and thereaction product being different.

The copolymer reaction product of the present invention is useful in amethod of flushing a pigment of the type wherein water in an aqueousmass of pigment is flushed with a low molecular weight polymer. Theimprovement comprises flushing the aqueous mass of pigment with at leastone copolymer reaction product of the present invention resulting in apigmented composition.

The pigmented composition of the present invention can be used in a widevariety of compositions where the pendant amide chains on the reactionproduct enhance compatibility. A particularly useful composition is acomposition comprising the pigmented composition and a polyamidepolymer. Such compositions have excellent uniformity of pigmentdistribution. More importantly, the pigmented composition results in apolyamide composition with uniform pigment distribution evidenced byuniform and enhanced color. The color is actually enhanced by morecomplete pigment dispersion.

DETAILED DESCRIPTION OF THE INVENTION

The present invention includes a copolymer reaction product of a lowmolecular weight copolymer of an unsaturated acid and an α-olefin, andan amino acid compound resulting in a copolymer having pendant amidechains including polyamides, and a method to make the reaction product.The present invention also includes a polymer composition, and apigmented composition which comprise the copolymer reaction product, aswell as compositions which comprise the pigmented composition. Thepresent invention further includes a method of flushing pigments withthe copolymer reaction product.

Copolymers useful to make the copolymer reaction product of the presentinvention include the copolymer of an α-olefin and an unsaturatedcarboxylic acid, preferably an α,β-ethylenically unsaturated carboxylicacid or derivative thereof. These copolymers are of low molecularweight, having a number average molecular weight of from about 500 toabout 6,000, and preferably about 1,000 to about 3,500. Useful andpreferred copolymers include homogeneous copolymers of ethylenedisclosed in U.S. Pat. No. 3,658,741, the disclosure of which is herebyincorporated by reference.

The α-olefin preferably has from 2 to 8 carbon atoms and is mostpreferably ethylene or propylene. There is at least about 50, preferablyfrom about 50 to about 99.5, more preferably, about 65 to about 99.2,and most preferably from about 80 to about 98 mol percent of theα-olefin, which is most preferably ethylene.

The unsaturated carboxylic acid or derivatives thereof includes suchcompounds disclosed in U.S. Pat. No. 3,658,741. Useful carboxylic acidsinclude both monocarboxylic and polycarboxylic acids and derivativesthereof, including esters and anhydrides, which are capable of reactingwith the amino acids recited below. Useful carboxylic acids orderivatives thereof include unsaturated monocarboxylic acid containingfrom 3 to 6 carbon atoms and dicarboxylic acids containing from 4 to 8carbon atoms. Specific examples of unsaturated acids copolymerizablewith ethylene include acrylic acid, methacrylic acid, ethacrylic acid,itaconic acid, crotonic acid, maleic acid and fumaric acid. Also usefulare acid halides, amides and esters including acrylyl chloride andacrylamide. Esters which can be used include methyl acrylate, methylmethacrylate, ethyl acrylate and dimethylaminoethyl methacrylate. Alsouseful are monoesters of dicarboxylic acids, such as methyl hydrogenmaleate, methyl hydrogen fumarate, ethyl hydrogen fumarate, and maleicanhydride. Particularly preferred compounds include α,β-ethylenicallyunsaturated acids and derivatives thereof.

A preferred copolymer acid is a copolymer of ethylene and anα,β-ethylenically unsaturated mono-carboxylic acid having 3 to 6 carbonatoms. A most preferred α,β-ethylenically unsaturated mono-carboxylicacid is acrylic acid. Most preferred is ethylene acrylic acid copolymerwhich has an acid number in the range from about 1 to about 180, with anacid number from about 40 to 160 being preferred, and an acid numberfrom about 40 to 120 being most preferred. The acid number is determinedby the number of milligrams of potassium hydroxide needed to neutralizeone gram of acid. The number average molecular weight is from about 500to about 5000, and preferably from about 1000 to about 3500. Table Ibelow characterizes preferred ethylene acrylic acid copolymers.

                                      TABLE I                                     __________________________________________________________________________          Softening Pt.                                                                        Hardness                                                                            Density                                                                           Brookfield                                                                          Acid No.                                                                           Wt %                                        Copolymer                                                                           (ASTM E-28)                                                                          dmm   g/cc                                                                              Viscosity @                                                                         mg   Acry-                                       Acid  °C.                                                                       °F.                                                                        (ASTM D-5)                                                                          D-1501                                                                            140° C. cps                                                                  KOH/g                                                                              lic                                         __________________________________________________________________________    A     108                                                                              226 2.0   0.93                                                                              500   40   5                                           B     101                                                                              215 4.0   0.93                                                                              650   75   9.4                                         C      92                                                                              198 11.5  0.93                                                                              650   120  15                                          __________________________________________________________________________

The copolymer acids are available from AlliedSignal Inc. as A-C®540(A);A-C®580(B) and A-C®143(C).

The low molecular weight copolymer acids can be prepared by any suitablemethod such as described in above referenced U.S. Pat. No. 3,658,741. Ofparticular interest in U.S. Pat. No. 3,658,741 is the passage beginningat column 7, line 36 through column 8, line 6. In accordance with thisprocess, the ethylene desirably constitutes at least 65% by weight ofthe monomer feed and the comonomer from 1.0% to 35% of the feed,preferably 2 to 20% by weight of the feed. Under specific conditions ofvapor phase polymerization the ratios by weight of the monomers in thefeed and in the product are substantially constant. The ratio ofcomonomer between feed and product are at most only minor such thatproducts obtained by the invention contain a major portion of ethyleneand generally 0.8% to 35% by weight of the comonomer, preferably 2.0% to20% by weight of the comonomer. The ratio of comonomer in the product tocomonomer in the feed is preferably within the range of 0.7:1 to 1.8:1.

The acid copolymers useful in the present invention are of low molecularweight ranging generally between about 500 to about 6000 number averagemolecular weight, preferably between about 1000 to about 3500 numberaverage molecular weight, as measured by a vapor pressure osmometer. Thecopolymers also desirably have a Brookfield viscosity not exceedingabout 2000 centipoises at 140° C., preferably between about 200 to about1200 centipoises at 140° C. Of special interest are the copolymers ofethylene and acrylic or methacrylic acid containing from about 1% toabout 20% by weight acrylic acid or methacrylic acid in the copolymer,preferably about 3.5% to about 12%, and further characterized by anumber average molecular weight between about 1500 to about 3500, acidnumber between about about 10 to about 200, preferably about 20 to about130, and hardness (0.1 mm penetration) between 0.5 to 30, preferably 1to 10 when tested at room temperature about 25° C. (77° F.) according toASTM D-5 using a needle with a load of 100 grams for 5 seconds.

In accordance with the present invention up to 100, preferably fromabout 50 to about 100 and more preferably about 10 to about 30 percentof the carboxylic acid groups are reacted with from about 0.1 to about50, preferably, 0.1 to 40, more preferably about 0.5 to about 30, andmost preferably about 5 to about 25 weight percent based on the weightof the reaction product of at least one amide chain derived from atleast one amino acid compound. There can be from about 10 to about 30,or about 0.1 to about 10 weight percent of at least one amide derivedfrom at least one amino acid. For the purpose of the present inventionamino acid compounds include: amino acids, and cyclic amides, i.e.,lactams which can be hydrolized to form amino acids; and derivativesthereof.

Preferably, the amino acid compound is an amino acid monomer which hasthe formula H₂ NCH₂ (CH₂)_(n) COOH where n is from 0 to 12, and morepreferably from 4 to 8; or an amino acid oligomer or polymer derivedfrom this monomer. The most preferred amino acid monomer is aminocaproic acid or its lactam, caprolactam.

Also useful amino acid compounds are derivatives of the amino acidsincluding esters, or lactams of the amlno acids. Specific examples ofuseful amino acids include ε-amino-caproic acid; 11-aminoundecanoicacid; 12-aminododecanoic acid; esters, amides and lactams ofmonoamino-monocarboxylic acids, such as ε-caprolactam; ethylε-aminocaproate; lauryl lactam; ethyl-11-aminoundecanoate;11-aminoundecanoamide, and the like. The amino acid can be a polyamide,such as, polycaprolactam. Alternatively, the polyamide can be apolyamide of the type made from a diamine and a dicaboxylic, such aspoly(hexamethylene adipamide), i.e., nylon 66.

The reaction between the amino acid compound and the acid copolymerresults in grafts having the formula ##STR1## wherein x is from at least1, and preferably 1 to 250, and R can comprise at least 2 methylenegroups and preferably from 4 to 8 methylene groups; or be the radical ofa diacid/diamine polyamide.

The average amide chain length reacted at each carboxyl site ispreferably from about 1 to about 250, preferably 1 to 200, with specificembodiments including amide chain lengths of from 1 to 10, and 1 to 5amide groups. There can be longer amide chain lengths of from 100 to 250amide groups. Preferably, there are sufficient amide grafts, ofsufficient length to confer compatibility of the copolymer reactionproduct and another polymer, preferably polyamide. For the purpose ofthe present invention amino acid compounds include cyclic amides, i.e.,lactams which can be hydrolized to form an amino acid compound. Apreferred amino acid compound has the formula H₂ NCH₂ (CH₂)_(n) COOHwhere n is from 0 to 12, and more preferably from 4 to 8. The mostpreferred amino acid is amino caproic acid or its lactam, caprolactam.

The copolymer reaction product of the present invention is characterizedby an acid number of from about 10 to about 200, preferably about 25 toabout 150, and most preferably about 25 to about 75 where the acidnumber is the number of milligrams of KOH used to neutralize one gram ofsample. The copolymer reaction product has a Brookfield viscosity at140° C. of from about 500 to about 5,000, preferably about 500 to about2,000, and more preferably about 500 to about 1,500. The Mettler droppoint according to ASTM D-3104 can be at least about 90° C., and can befrom about 90° C. to about 150° C.

The present invention includes a method for preparing the above recitedcopolymer reaction product comprising the steps of heating a copolymerof α-olefin and an α,β-ethylenically unsaturated carboxylic acid to fromabout 110° C. to about 300° C., preferably about 150° C. to about 275°C., and more preferably about 200° C. to about 275° C.; adding asufficient amount of at least one amino acid compound to react with upto 100 and preferably 50 to 100 percent of the carboxylic acid groups;and conducting the reaction of the copolymer and the amino acidcompound. Preferably, the copolymer acid is preheated to from about 110°C. to about 200° C. and more preferably, about 125° C. to about 175° C.prior to reaction with the amino acid compound.

The reaction is preferably conducted under an inert atmosphere, such asnitrogen or argon, or under a vacuum. The reaction pressure is notcritical and is preferably conducted at about 1 atmosphere. The reactioncan be conducted continuously or in batches.

The present invention also includes a polymer composition comprising atleast one first polymer, and at least one second polymer comprising theabove recited copolymer reaction product. The polymer compositioncomprises up to 99 percent and preferably from 1 to 99 percent of atleast one first polymer and a corresponding amount of the reactionproduct. The reaction product can lubricate the first polymer consistentwith polymer lubrication recited in U.S. Pat. No. 4,412,040. The firstpolymer is different from the second polymer.

The first polymers include but are not limited to polyamides, such asnylon 6, nylon 66, nylon 4, nylon 11, nylon 12 and like; polyolefins,such as polyethylene and polypropylene; styrene based polymers, such aspolystyrene; polyesters, such as polyethylene terephthalate andpolybutylene terephthalate; ABS (copolymers of acrylonitrile, butadieneand styrene); polycarbonates; phenolic resins.

The present invention includes a pigment composition comprising fromabout 1 to about 50, preferably from about 5 to about 40, and morepreferably from about 15 to about 35 weight percent of above-recitedcopolymer reaction product; from about 1 to about 50, and morepreferably from about 5 to about 40 weight percent of a pigment; andfrom 0 to 98 weight percent of the first polymer. The pigmentcomposition is useful in polymer compositions for molded and extrudedgoods, films and fibers, inks and the like. The reaction product byvirtue of improved compatibility with the first polymer improves pigmentdispersion consistent with improved dispersion properties recited inU.S. Pat. No. 4,603,172.

Typical pigments include: titanium dioxide, zinc oxide; calciumcarbonate; barite, silica and china clay; lead white; carbon black; redlead; chromate pigments; Venetian Red; Prussian blue; chromic oxide;chrome green; cobalt blue, Phthalo blue, Phthalo green, and azopigments.

There can be from about 0.1 to about 100 parts per hundred parts ofpolymer of the pigment to be dispersed. Preferably there is about 0.1 toabout 50 parts of the material. Lower concentrations of from about 0.1to about 1 part per hundred parts of polymer are useful for directblending of low concentration materials such as colorants. Higherconcentrations of from greater than about 10 parts of material can bedirectly introduced into the polymer. High concentrations of from about10 to about 50 parts of material per hundred parts of polymer are usefulto make master-batches, such as color concentrates, for introductioninto larger quantities of the same or different polymers.

The composition can comprise conventional additives such as colorantsincluding fillers, flame retardants, antioxidants, stabilizers,processing aids, and the like.

Typically, fillers may be selected form a wide variety of minerals,metals, metal oxides, siliceous materials, metal salts, and materialsthereof. Examples of fillers include glass fibers, alumina, feldspar,asbestos, talc, calcium carbonates, clay, carbon black, quartz,novaculite and other forms of silica, kaolinite, bentonite, garnet,mica, saponite, wollastonite, etc. The foregoing recited fillers areillustrative only and are not meant to limit the scope of the fillersthat can be utilized in this invention.

The copolymer reaction product of the present invention is useful in amethod of flushing a pigment, of the type wherein water in an aqueousmass of pigment is flushed away with a low molecular weight polymer. Theimprovement of this invention comprises flushing the aqueous mass ofpigment with at least one copolymer reaction product of the presentinvention.

In the flushing process an aqueous pigment mass comprising finelydivided pigment is in the form of a filter press cake having from about25 to about 60, and more typically from about 30 to about 45 weightpercent of pigment with a corresponding amount of water. The lowmolecular weight copolymer reaction product is added in a mixing meanssuch as a Sigma blade mixer in amounts as recited above. Preferably,there is (based on the weight of pigment) from about 25 to 75, and morepreferably from about 40 to about 60 percent by weight of the aqueouspigment mass and a corresponding amount of the low molecular weightcopolymer reaction product. The mixture is heated until the waterseparates from the pigment and the low molecular weight reactionproduct, typically at about 90° C. to about 110° C., preferably, about90° C. to about 100° C., and most preferably, about 90° C. to about 95°C. The process typically takes from 10 to 120 minutes and more usually15 to 30 minutes. At this point a drop in power to the mixer will beobserved. The mixing is continued for a few more minutes, typically 2 to5 additional minutes. The water in the mixer is decanted. A vacuum canbe applied to remove the balance of the water. This leaves behind auniform blend of the pigment and the low molecular weight copolymerreaction product. The process of flushing can be conducted batchwise orcontinuously with filter press cake and copolymer reaction productcontinuously or intermittently added as the water is decanted. Theprocess has resulted in a high quality dispersion of the pigment in thecopolymer reaction product.

The flushed pigments result in pigment concentrates which can be furtherdiluted with a first polymer of the type recited above to make pigmentmaster batches. Such dilution can be accomplished by melt blending in asuitable melt blender, such as an extruder. The pigment master batchtypically has from 40 to 80 weight percent of a first polymer andcorrespondingly from 20 to 60 weight percent of the pigment concentrate.

The flushed pigments in the form of pigment concentrates and in pigmentmaster batches are useful in polymeric compositions used for fibers,molding compounds, extrusion compounds, sheets, film, and the like.

The examples set forth below illustrate the nature of the invention andthe manner of carrying it out. However, the invention should not beconsidered as being limited to the details thereof.

EXAMPLE 1

This example illustrates the copolymer reaction product of the presentinvention based on an ethylene acrylic acid copolymer B of Table 1, soldby Allied-Signal Inc. as A-C®580. This copolymer acid is reported tohave an acid number of 71.9. 4361 grams of A-C®580 were melted in atwelve liter flask. A nitrogen atmosphere was maintained at all times.The copolymer was heated to 116° C., at which time 713 gms of6-aminocaproic acid powder was added. The mixture was continuallystirred. The temperature was increased and at 149° C. the evolution ofwater was observed. The water was allowed to distill. At 156° C. waterwas evolving vigorously. The temperature was then maintained at160°-162° C. for three hours. After three hours at 160° C., the flaskwas discharged, at which point the material had an acid number of 65.1.Acid number is based on the milligrams of KOH needed to neutralize agram of sample.

EXAMPLE 2

Pilot plant runs were made to make the copolymer reaction product of thepresent invention. The copolymer acid used was A-C®580 described above.The amino acid used was a polycaprolactam having a number averagemolecular weight of about 18,000, and a formic acid viscosity of about50. Where indicated the polycaprolactam contained minor amounts of heatstabilizers. The polycaprolactam was a straight chain polymer terminatedat one end with an amine group and at the opposite end with a caboxylicacid group.

A charge of 550 pounds (250 kg) copolymer acid was first premelted in a200 gallon (0.76m³) tank at 145 to 150° C. under a nitrogen sweep atabout 1 atm.

The molten copolymer acid was fed to a 200 gallon (0.76m₃), stirredreactor which had a condenser to remove moisture flashing off during theformation of the reaction product. The copolymer acid was heated toabout 158° to 162° C. and 155 pounds (70 kg) of the polycaprolactam wasgradually added. The reactor was closed and heating continued to 260° C.for eight hours with agitation.

Seven batches were made using the stabilized polycaprolactam (Runs 1-7)and two batches were made using the same polycaprolactam withoutstabilizers (Runs 8,9). Results are reported in Table 2 below.

                  TABLE 2                                                         ______________________________________                                                                      METTLER                                              PARTS    Rx              DROP    BROOKFIELD                                   PER 100  TEMP    ACID NO.                                                                              POINT   VISC. @                                 RUN  AC580    (°C.)                                                                          (°C.)                                                                          (°C.)                                                                          140° C. (Cps)                    ______________________________________                                        1    28.2     250     54.4    96.2    1575                                    2    28.2     270     54.5    97.0    1730                                    3    28.2     260     54.3    96.8    1520                                    4    22.6     250     57.1    96.6    1488                                    5    17.0     250     60.5    96.1    1375                                    6    28.2     250     54.9    95.3    1562                                    7    28.2     260     54.5    95.6    1542                                    8    28.2     260     54.9    96.1    1777                                    9    28.2     260     55.3    96.2    1825                                    ______________________________________                                    

EXAMPLE 3

The procedure of Example 2 was repeated resulting in a reaction producthaving an acid number of 51.1; a Brookfield viscosity at 140° C. of 1168centipoise; and a Mettier Drop Point of 100.7° C.

The copolymer reaction product had a uniform and white appearance. Thefeel was that of a hard waxy material. As indicated by the relativelylow Mettler Drop Point values, this material is readily melt blendablewith other polymers.

While exemplary embodiments of the invention have been described, thetrue scope of the invention is to be determined from the followingclaims.

What is claimed is:
 1. In a method of flushing a pigment, of the typewherein water in an aqueous mass of pigment is flushed with a lowmolecular weight polymer, the improvement comprising flushing theaqueous mass of pigment with at least one copolymer reaction product ofa copolymer acid of an α-olefin and an α,β-ethylenically unsaturatedcarboxylic acid, the copolymer acid having a number average molecularweight of from about 500 to about 6,000 reacted with from about 0.1 toabout 30 weight percent of at least one amino acid compound based on theweight of said reaction product.
 2. The method of claim 1 wherein theamino acid compound is derived from an amino acid monomer of the formulaH₂ NCH₂ (CH₂)_(n) COOH where n is from 0 to
 12. 3. The method of claim 2where n is from 4 to
 8. 4. The method of claim 3 where the amino acidmonomer is aminocaproic acid.
 5. The method of claim 1 where theα-olefin is selected from ethylene and propylene.
 6. The method of claim5 where the α-olefin is ethylene.
 7. The method of claim 1 where thecarboxylic acid is an α,β-ethylenically unsaturated carboxylic acid. 8.The method of claim 7 where the α, β-ethylenically unsaturatedcarboxylic acid is selected from acrylic acid, methacrylic acid,crotonic acid, maleic acid and fumaric acid, and mixtures thereof. 9.The method of claim 7 where the α,β-ethylenically unsaturated carboxylicacid is acrylic acid.
 10. The method of claim 1 where there is fromabout 10 to about 30 weight percent of the amino acid compound.
 11. Themethod of claim 1 where there is from about 0.1 to about 10 weightpercent of the amino acid compound.
 12. The method of claim 1 whereinthe copolymer comprises about 65 to about 98 mol percent of the α-olefinand about 2 to about 35 mol percent of the α,β-ethylenically unsaturatedcarboxylic acid.
 13. The method of claim 12 wherein from about 50 toabout 100 mol percent of the carboxylic acid groups are reacted with theamino acid compound.
 14. The method of claim 1 where the amino acidcompound has an average chain length at each carboxyl site of from about1 to about 250 amino acid monomer units.
 15. The method of claim 1 wherethe amino acid is a polyamide.